Acetabular dysplasia at the age of 1 year in children with neonatal instability of the hip: A cohort study of 243 infants

BACKGROUND AND PURPOSE: As much as one-third of all total hip arthroplasties in patients younger than 60 years may be a consequence of developmental dysplasia of the hip (DDH). Screening and early treatment of neonatal instability of the hip (NIH) reduces the incidence of DDH. We examined the radiographic outcome at 1 year in children undergoing early treatment for NIH. SUBJECTS AND METHODS: All children born in Malmö undergo neonatal screening for NIH, and any child with suspicion of instability is referred to our clinic. We reviewed the 1-year radiographs for infants who were referred from April 2002 through December 2007. Measurements of the acetabular index at 1 year were compared between neonatally dislocated, unstable, and stable hips. RESULTS: The incidence of NIH was 7 per 1,000 live births. The referral rate was 15 per 1,000. 82% of those treated were girls. The mean acetabular index was higher in dislocated hips (25.3, 95% CI: 24.6–26.0) than in neonatally stable hips (22.7, 95% CI: 22.3–23.2). Girls had a higher mean acetabular index than boys and left hips had a higher mean acetabular index than right hips, which is in accordance with previous findings. INTERPRETATION: Even in children who are diagnosed and treated perinatally, radiographic differences in acetabular shape remain at 1 year. To determine whether this is of clinical importance, longer follow-up will be required.